4 in 7

Chance the Democrat wins (56.6%)

3 in 7

Chance the Republican wins (43.4%)

us_map2See the national overview
Forecasted turnout
Partisan lean

# What goes into the
icon_classic_2
classic forecast in the California 48th

The Classic version of our model projects a race’s outcome by taking a weighted average of polls of a district (if available), polls of similar districts (CANTOR) and non-polling factors (fundamentals). It is then reverted toward a mean based on long-term trends in midterms and presidential approval ratings.

  • R+1.5

    Adjusted polls

  • R+4.1

    CANTOR

  • D+8.8

    Fundamentals

  • D+4.1

    Experts

  • R+1.5

    icon_lite_2

    Lite

  • D+1.1

    icon_classic_2

    Classic

  • D+2.1

    icon_deluxe_2

    Deluxe

  • <0.1

  • <0.1

Historical adjustment

Key

More weight

Less

#Latest polls

We've collected seven polls for the California 48th. We’re adjusting poll results in three ways: Polls of registered voters or all adults are adjusted to a likely-voter basis; older polls are adjusted based on shifts in the generic congressional ballot since the poll was conducted; and polls are adjusted for house effects (the tendency for a firm’s polls to lean toward Democrats or Republicans). Polls with larger sample sizes and those conducted by higher-quality polling agencies are given more weight, as are more recent polls.

Adjustments
datespollstersampleweight
Rouda
Rohrabacher
marginlikely voterTime-lineHouse effects Adjusted margin
Oct. 29-Nov. 4
10/29-11/4
Siena College/New York Times491LV
1.78
46%45%D+1.7 <0.1 0.3 D+1.5
Oct. 30-31
10/30-31
Thomas Part­ners Strategies 440LV
0.92
42%51%R+9.1 <0.1 3.6 R+5.5
Oct. 17-21
10/17-21
Monmouth University372LV
0.66
48%50%R+2.0 <0.1 0.2 R+2.2
Oct. 18-19
10/18-19
Thomas Part­ners Strategies 440LV
0.26
41%49%R+7.8 <0.1 3.6 R+4.2
Sep. 16-23
9/16-23
UC Berkeley623LV
0.13
48%48%EVEN 0.1 2.1 R+2.2
Sep. 4-6
9/4-6
Siena College/New York Times501LV
0.01
45%45%EVEN 0.1 0.3 R+0.4
Jul. 11-15
7/11-15
Monmouth University361LV
0.00
48%44%D+3.3 0.6 0.2 D+3.7
Weighted averageR+1.5

Key

A = adults

RV = Registered voters

V = voters

LV = likely voters

R
D

= partisan poll

Our latest coverage

#Similar districts and CANTOR

Our district similarity scores are based on demographic, geographic and political characteristics; if two districts have a score of 100, it means they are perfectly identical. These scores inform a system we use — CANTOR, or Congressional Algorithm using Neighboring Typologies to Optimize Regression — to infer what polling would say in unpolled or lightly polled districts, given what it says in similar districts.

Districts most similar to the California 48th
Sim. score Polling avg.
CA-4969D+9.8
CA-4562D+0.5
CA-3960R+1.2
AZ-656R+14.3
CA-5255
NV-353D+9.4
CO-652D+8.4
CA-747D+14.4
CA-2544R+3.7
TX-3244D+3.2

#The “fundamentals”

The Classic and Deluxe versions of our model use several non-polling factors to forecast the vote share margin in each district.

FactorImpactExplanation
Incumbency
1.9
Dana Rohrabacher has been elected to 15 terms. Congress has only a 20.1% approval rating, reducing the incumbency advantage.
District partisanship
1.4
CA-48 is 6.7 percentage points more Republican-leaning than the country overall, based on how it has voted in recent presidential and state legislative elections. It voted for Clinton in 2016 and Romney in 2012.
Incumbent's margin in last election
3.8
Rohrabacher won by 16.6 percentage points in 2016.
Generic ballot
4.2
Democrats lead by an average of 8.6 percentage points in polls of the generic congressional ballot.
Fundraising
3.5
As of Oct. 17, Harley Rouda had raised $5,014,000 in individual contributions (73% of all such contributions to the major-party candidates); Rohrabacher had raised $1,882,000 (27%).
Incumbent's voting record in Congress
1.1
Rohrabacher has voted with Republicans 85% of the time in roll-call votes in recent sessions of Congress. Candidates who vote with their party very frequently tend to underperform at the ballot booth, other factors held equal.
Challenger experience
0.4
Rouda has never held elected office.
Scandals
5.1
Rohrabacher is involved in a scandal that developed since the last election for this seat.
Top-two primary margin
2.6
Republicans won the aggregate vote by 7.0 percentage points in the June primary. However, turnout patterns can differ in the general election, so the model compares the primary result to others in California. On that basis, it treats the primary result as equivalent to a 6.5-point win for Democrats.
Total
D+8.8

#Expert ratings

The Deluxe version of our model calculates an implied margin for each race based on expert race ratings from The Cook Political Report, Inside Elections and Sabato's Crystal Ball; it then adjusts that margin toward its estimate of the national political environment.

Equivalent Margin
ExpertRatingRaw Adjusted
Cook Political Report
Toss-up
EVEND+0.6
Inside Elections
Tilt D
D+4.4D+5.3
Sabato's Crystal Ball
Leans D
D+6.7D+6.3
AverageD+3.7D+4.1

How this forecast works

Nate Silver explains the methodology behind our 2018 midterms forecast. Read more …

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